Hydromechanical power transmission drive



June 10, 1952' w. CULI. 2,599,814"

HYDROMECHANICAL POWER TRANSMISSION DRIVE Filed Nov. 25, .1945 4 sheets-sheet 1 `lune 10, 1952 w. CULL HYDROMECHANICAL POWER TRANSMISSION DRIVE 4 Sheets-Sheet 2 Filed NOV. 23, 1945 F/Gl.

4 Sheets-Sheet 3 Filed Nov. 25, 1945 June 10, 1952 W. CULL HYDROMECHANICAL POWER TRANSMISSION DRIVE 4 Sheets-Sheet 4 FIG. 5.

Filed Nov. 25, 1945 7 mv. F

Patented June 10, 1952 HYDROMECHANICAL POWER TRANS- MISSION DRIVE William. Cull., Utley, Keighley, England Application November 23, 1945*, Serial No. 630,451 In Great Britain June 19, 1943 Section 1, Public Law 690, August8, 194,6` Patent expires June 19,1963y 12 Claims.

This. invention relates. to hydromechanical power transmission drives wherein the ratio betweenthe powerorenginetorque and the driving torquehastobe varied to suit varying conditions andloads encountered. While. the invention will be. described. as applied to road and rail Vehicles it-w.ill.\b`e understood that it is applicable to all forms of drive such as for instance machine. tools where. the. power. and driving torque ratio has to be variedtosuitworkingconditions.

Hitherto this. has been'eifected'by numerous methodssuch as. asimple boxgiving. predetermined` ratios. adapted to'be. selected 4by the gear lever and comprising. either meshing'v gear trains or epicyclic gearing.`

YHydraulic constructions have been proposed wherein. a hydraulic. differential is coupled to a differential` gear assembly, the hydraulic differential-c'omprising pump and motor units mounted co-.axially in. a common casing. which is adapted to.. revolve unidirectionally about the axis of the two` units. The pump and motor units revolve inthe same direction so that the speed of the outputshaft is varied by altering the capacity ratios ofthe two hydraulic units.

A further method has been. suggested by which a combined electricall and mechanical transmissionf' isemploy'ed for producing a continuously variable ratio between the engine torque and driving'- torque or resistance based upon a differentialv action between directly transmitted mechanicalf power and a D. C. electric machine and consumed by another. The driving torque and consequently the torque ratio is` controlled by conventional use of the acceleration vpedal and its variation is produced by a small generator whose speed is proportionate to the vehicles speed.

' TheA chief object of the present invention is to provide a transmission system wherein an innnitelyvariable gear ratio is obtainable with attendant torque multiplaction without the use of! electrical apparatusv with the result that a simpler land more efficient driving transmission is possible.

According to the invention the hydro-mechanical'f powertransmission drive comprises a variable ratio torque converter wherein one hydraulic uni't'ls'in driving connection with the input gear of an epicyclic train this unit being'arranged to have a variable capacity from maximum plus to maximum minusthrough zero so as to be'V operable either as a pump or a motor and another hydraulic unit in hydraulic connection with said first mentioned hydraulic unit 'and in driving connection with the abutment or reaction. lgear 2l adapted to operate in such a manner that. at all times the torque at the input gear ofthe epicyclic train isthe algebraicsum ofl'the. engine torque.

and the hydraulic torque furnished by the reaction between the two hydraulic units by reason of their respectivecapacity ratios.

The driving torque. and therewith the torque ratio, as in the case. of a motor road vehicle,'is controlled by conventional use ofthe acceleration pedal, and its variation is effected by a hydraulic governor whose speed is proportionate to the vehicle speed. The' torque ratio referred to is the ratio between input. and output torques which equals the gear ratio with efficiency. The gear unit may comprise a planetary unit having a ring gear driven from the engine or power unit of the vehicle by way ofthe input shaft, planet gears mounted upon a carrier associated with the output shaft of the vehicle's drivingwheels, and a sun gear mounted upon a hollow shaft which eri-closes the output shaft.

A hydraulic unit hereafter referred. to as the torque unit is driven by the sun gearY shaft'and may comprise a hydraulic pump which can either deliver, pump, or be driven Ias a motor, such Vas either the radial inward type with an eccentric shaft, radial outward type with an eccentric race or a single or opposed swash plate. motor. Any rotary or reciprocal hydraulic motor is suitable providing it can both deliver or pump and be driven.

A further hydraulic unit hereafter called the regulator is associated with the input shaft and comprises any rotary or reciprocal hydraulic unit which can either deliver and pump or be driven by reason of its Variable capacity from maximum plus to maximum minus through zero.

The torque and regulator units are coupled hydraulically. in a closed circuit, arranged to be fed through non-return make upv valves by a small auxiliary pump driven from the input shaft and arranged to maintain a pressure of 50 lbs. or more in the closed circuit; The two halves 0f the circuit are bridged by a by-pass valve which is arranged to by-pass the regulator unit 'on depression of a pedal with the yresult that the latter pedal can take the place of the conventional clutch. Incorporated'in'this by-pass valve is a two-way relief valve designed so as to lift from its seat if the pressure on either'side of the circuit reaches a predetermined maximum and in so doing lay-passes the regulator unit. This relief valve provides a safety device inthe circuit and serves by` its setting to limit the. maximum torque at the output shaft to any pre-set value, which is a valuable feature in the case of, autoon the input shaft 2.

mobile transmissions, as the maximum acceleration can be kept within pre-set limits.

Preferably the capacity or strokes of the regulator unit will be variable from plus to minus through Zero to give an effective range in conjunction with the planetary unit from low to high gear. The capacity range of the regulator Y unit is actuated or controlled from a control unit influenced by a couple, one force acting from or influenced by the uid pressure in the connecting pipe or hydraulic main between the torque unit and the regulator unit and the other or balancing force by fluid pressure from a governor unit driven by the output shaft of the transmission.

If desired a third force may be applied to'the central unit to act as a steadying or balancing medium and be actuated by a hydraulic governor driven by the engine or power unit of the vehicle. This would also limit the maximum revolutions per minute of the engine or power unit thus ensuring" the optimum condition throughout the engineV gear combination in maximum useful torque. Y

A convenient capacity relationship or ratio of the regulator unit maximum volume compared with the torque unit maximum volume will be substantially the same as the number of teeth on the ring gear compared with the number of teeth on theV sun gear but this is not essential.

`In order that the invention may be clearly understood and readily carried into effect the same will now be more fully described with reference to and by the aid of the accompanying drawings, wherein:

Figure l is a diagrammatic illustration of the invention as applied to a transmission suitable for use on a motor road vehicle.

Figure 2 is a diagrammatic View of an alternative layout of gear unit.

Figure 3 is a sectional elevation of a hydromechanical Vgear constructed in `accordance with the invention.

Figure 4 is a sectional plan showing the servo actuating mechanism and one trunnion of the swash plate.

Figure 5 is a detail sectional view of the nolap valve and its associated parts.

Figure 6 is a detail sectional View of the servo valve and its associated parts and is taken on the line B-B of Figure 7, and

Figure '7 is a sectional view taken substantially along the line A--A of Figure 6.

Referring to Figures l and 2 of the drawings the transmission comprises a gear unit I of the epicycli-c or planetary type wherein the output shaft 2 from the engine (not shown) or input to the gear unit I is connected to a ring gear 3 and the planet pinions 4 are mounted upon a carrier 5 driving the output shaft 6 to the rear axle (not shown) of the Vehicle. A sun gear 'I meshing with the planet pinions 4 is mounted on a hollow shaft 8 through which the output shaft 6 passes. Mounted upon the sun gear shaft 8 or in driving connection therewith is a dual purpose hydraulic torque unit 9 comprising a swash plate motor connected through suitable valves by fluid pipe lines 10a and I 0b to a hydraulic regulator unit I I The latter unit I I is also of Vthe swash plate type but the swash plate I2 on the input shaft 2 is adjustable so that the stroke of the pistons I3 can be varied from maximum plus to maximum minus through zero in which latter position no movement of the pistons I3 is possible.

The two units, 9, II, respectively are coupled through suitable valve chests (not shown) in a closed circuit'IUa, IUb as shown, by which arrangement one fluid pipe Ina becomes a high pressure main and its opposite or return pipe Ib becomes a low pressure main, forming the two halves of the circuit which are separated by the hydraulic units 9 and Il. The high and low pressure mains Illa, Ib are brought into a valve unit I4 comprising a piston valve I5 which may connect the high and low pressure mains Ia, Ib by way of the extension pipe lines Illa: and Iy, thus by-passing either of the hydraulic units so that when the torque or regulator unit or both are revolving no power is transmitted to the output shaft 6. due to the oil being by-passed through the valve I 5. This valve I 5 can be operated by a foot-pedal I6 or a hand lever (not shown) and the unit can thus be arranged to take the place of the transmission or friction clutch in a conventional automotive transmission.

. Incorporated in the by-pass valve I5 is a twoway reliefV valve II which relieves both sides of the hydraulic system and is arranged to by-pass oil from either side of the circuit to the other should the pressure in either side exceed a pre,- determined maximum; thus the torque on the output shaft 6 (which is porportional to the pressure in the hydraulic main) is limited to a safe value either on the drive or over-run, and this has many advantages apart from protecting themechanism such as the ability to limit by the valve II setting the maximum acceleration of any vehicle to which the gear might =be fitted.

An additional fluid pipe I8 leads from the high pressure main I0a to a control unit C comprising a cylinder I9 containing a piston 20 acting against a spring 2l, said piston 20 having a piston rod 22 connected to an auxiliary control unit or disc member 23 adapted to adjust or vary the position of the swash plate I2 of the regulator I I by means of a connecting rod 24 and lever 25V associated with the swash plate I2. The cylinder I9 and piston 20 for the present purpose will be called the low gear control.

A further cylinder 26- and piston 21 having a piston rod 28 hereinafter referred to as the high gear control acts upon the auxiliary control unit 23 in a similar and opposite manner to the low gear control and is supplied with oil at a pressure proportional to the speed of the driven shaft 6 through speed sensitive Igovernor unit 29 driven from the said driven or output shaft 6 comprising a no lap valve 30 operated by governor weights 3I and Vto which oil is supplied under pressure from an engine driven pump 32 which draws oil from a make-up tank 33 by way of the pipe 35 and delivers through further pipes 35 and 36- to the valve 30. A no lap valve is a valve having no over-lap afforded by a waisted valve when the distance between the lands formed by the waist is equal to the distance between the lands of the coacting surface of the valve body. The fluid in the closed circuit of the high pressure main is maintained at a minimum pressure by means of the sprngloa-ded non return valves 31 fed from the pump 32 and pipe 35 should the pressure fall below the predetermined minimum. A third force may be applied to the control unit 23 by ampia through `'the governor weights l31| 4that are rotated by the output shaft 6. 'The valve member iis fre- Aduced or Waisted1at-82 to form a valve chamber 83 and beneath the yvalve member 89 is ga further chamber 84. The `chambers -83 and 8'4 are con- -neo'ted by a 4'duct 85. Inlet and exhaust ports 86 -andfll1, respectively, are formed in the valve body -"8=I and are Icapable of being closed by the valve 'member fBI). Itwill `be seen that when the speed of theoutput shaft It is increased, the valve member 80 is moved downwardly so as toropen vthe 'inlet port-'B6 :and close the lexhaust port 81,

with fthe result tha-t'fluid fis forced from Ythe pres- 'sure pump 32 l'through the pipes 35 and 36 and inlet 86 into-the chamber From this chamber -rthe fluid passes th-rough the duct 85 into the vchamber 184 andlintolthe lcylinder 26 of the control unitC.

The control unit C which includes the rotary member 23 serves to adjust or vary the position fof the swash plate I2 in accordance with the fluid `pressure in the `cylinders l19, 26 or 39. The cylinder I9 lis supplied A'with pressure fluid built up in rthe high pressure pipe Ita and constitutes the W or starting gear control and the iluid pressure operates on the spring-loaded piston 20 to `rotate the member 23. Opposed to the cylinder I9 and Y'spring-loaded piston 20 is the high gear, cylinder 26 which, a-s Lalready stated, receives uid pressure from the valve 'Syoperating in accordance with the vehicle spe-ed of the output shaft 6 to move the spring-loaded ypiston 21 and rotate the member 23 Iin an oppcs-iteldirection.

A third force which is in the nature of a balancing or damping force 'is applied to prevent sudden movements -cf the member 23 by the piston rod III and spring-loaded y'piston in the cylinder 39 to which fluid pressure is supplied from the piston and 1cylinder eng-ine Igovernor valve 38, this latter acting asa dash-pot.

v The pressures in cylinders I9 and 26 are equal because any pressure lin I9 is transmitted to 26 through the mechanical interconnection of the pistons 20 and 21 and vdue to the fact that the valve 30 has Closed the exhaust port 81.

The operation of the transmission shown diagrammatica-lly in Figure 1 is as follows: When the car is at rest and the 'engine turns over, the pressures in the low 'and high gear cylinders I9 and 2'6- are equal and the lswash plate I2 of the regulator IfI is at its central or zero position, and the valve I4 in 'the hydraulic system'is in the unloaded or `oy-pass position thus all oil displaced by the torque unit 9 is 'by-passed and there is no pressure difference across the hydraulic units 9 and I 1 other than that necessary to circulate the fluid.

The input shaft 2 and `ring gear 3 are rotating while the planet gear carrier 5 and output shaft 6 are stationary with the result that the sun gear 1 and its hollow shaft 8 are rotated in e. reverse direction to the input 2, and the valve vIll in the hydraulic lsystem is in the unloaded or by-pass position, thus all oil displaced by the torque unit 9 is by-passed andthere is no pressure difference across the hydraulic units 9 and II other than that necessary to circulatethe fluid. v

As the speed of the engine is increased by the conventional use of the accelerator pedal and the by-pass valve I 4 is closed by actuation of the foot pedal I', the rotation of the sun gear hollow shaft 8 operates the swashplate torque unit 9 and uid under pressure is forced along one of the high pressure fluid v,pipes 'I Da to the regulatorunit Il, but the swashplate I2 of this latter unit visl at itszzero position yso the nuid is ineffectual and incapable fof exerting :a driving .force in thecylinderrand von the piston I3 of the regulator unit Il, and the .pressure-in the high pressure pipe Illa is built up, thus increasing there-action between the :sun gear 1 .and the planet carrier 5 which tends to lturn theoutput shaft 6. pressure the high 'pressure fluid pipe Illa passes along Atof-'the A'connecting pipe .I8 to the low gear control cylinder |f9 with the result that the swashplate 'lf2 fof'ftheregulator unit .I I ismoved over gradualy lto the low :gear position by the piston 20 lthere Afleeing Jat `thisftime no appreciable pressure in the high gear cylinder as the vehicle is not yet moving --iZorW-ard, `except that maintained by the 'pump :32) and the latter unit II commences to be driven by the torque unit 9. Thus the torque A'onftlie ring Agear 3 `is the engine torque plus the regulator lunit Il `torque and this torque multiplication 1is:equivalent to low gear in a mechanical transmission.

'llfiefplanetcarrier 5 commences to revolve with 'the resu-ltfthat -`the vehicle moves forward. As lthe `speed -of l'thevehic'le increases, the rate of roftationo'f Ethe sun 4gear 1 decreases 'with resultant `decrease inflrotaition 4of the torque unit 9 and lowering -voi. pressure in the main fluid pipe Illa 'and Toy-pass pipe I8 to the low gear control. rllhiis, vand a rise in `pressure in the high gear con- 'trol 2S due -to the operation of the governor unit 'l2-9 from lthe output shaft 6, causes the swash plate I2 ofthe regulator unit I I to move over to -a higher gear and when theswash plate I2 passes 'zero the regulator unit I I changes its stroke and instead of being "a driven motor becomes a driving pump, and consequently the torque unit 9 slows down, con-ies to rr-est and commences to run in the opposite direction, lbeing driven by the regulator 'unit 14. IThis results in the gear unit I, namely the ring gear 3, ithelplanet carrier 5 and sun gear I'I rotating as one in the same direction to form ta direct vd-rive. As the output of the regulator unit II increases, so the speed of the torque unit 9 rises by reason of the capacity ratios between them and the rate oi' -rotation of the sun gear 1 is increased with-fthe result that an overdrive takeslplaoe.

The relative rotation and operation of the regu- 'la-tor unit l-'I and vtorque unit 9 and particularly the fluid pressure in the high pressure main Illa iis proportionate 'to the .resistance to be overcome at the road wheels. The 'pressure in the high gear cylinder Y26 is proportional to the square of speed of the vehicle v'because the pressure to control the cylinder 26 varies as the R. P. M. and is controlled by Ythe speed sensitive governor 29, thus vwhen the accelerator pedal is released andthe vehicle overruns the engine, e. g. the output shaft 6 is being driven by the road Wheels, the pressure in the high pressure main is considerably reduced, but as the vehicles speed is still the same, the pressure 'in the high gear cylinder 26 remains the same, thus the pressure diiferential 'across the control unit 23 is increased and the swashplate of the regulator unit is moved over into its highest gear position, with the result that the engine runs at a relatively low speed with a consequent 'saving in fuel.

Referring to Figures '3 and 4 of the drawings the transmission drive comprises a gear unit I ofthe epicycle or planetary type whose input shaft 2 is connected to the ring gear 3 andthe planetpniions 4 are mounted Aupon a carrier 5 driving the output shaft '6. A sun gear 1 meshing with `the planet pinions 4 is mounted upon a holl low shaft' through which the output shaft 6 passes. Mounted upon the sun gear shaft 8 is a dual purpose hydraulic torque unit 9. The torque unit comprises a non-rotating swash plate 4I engaged by pistons 42 in a rotating block 43 which carries Athe cylinders 44 of the motor or unit 9. The cylinders 44 are connected to' the high and low'pressure mains Ia and Ib through a valve chest 45 in the fixed casing 46. The pressure mains Ida and Ib lead to a hydraulic regulator unit I I also of the swash plate type having va nonrotating swash plate 'I2 -cooperating with pistons I 3 within a rotating cylinder'block 41 keyed to the input shaft 2 of the gear unit I.

The cylinder'block 41 abuts a valve chest 48 to which the highV and low pressure mains IUa-Ib are connected.

Thehigh pressure main Ia passes through a valve unit I4 comprising a piston valve I5 which may Yconnect the high and low pressure mains through the lay-pass port 49 and extension pipe ly, thusby-passing either ofthe tWo hydraulic units with the result that when the torque or regulator units 9 and I I or both are revolving no power is transmitted to the output shaft 6. The valve I is operated by a footpedal I 6 and can be arranged to take the place of the transmission or friction clutch for disengagement in a conventional automotive transmission. Incorporated in the by-pass valve unit I 4 is a two-way relief valve I1 arranged to ley-pass oil from either side of the circuit to the other should the pressure in either side exceed a predetermined maximum. In other words, the valve I1 by reason of its spring-loaded stepped piston opens and interconnects both 52 having a blind end, the piston 52 being acv commodated within a further cylinder bore 53.

The piston 5I and its associated cylinder 50 represent the low gear control whilst the piston 52 and its associated bore 53 represents the high gear control. Pressure fiuid is received in cylinder bore 53 from the speed sensitive governor valve driven from the output shaft 6 of the Y gear unit at vehicle speed. The pressure conduit from the valve 39 is tapped and connected to a pressure gauge adapted to read in miles per hour as 'thepressure in the conduit 3M is proportional to the speed of the vehicle. Also it will be seen that the pressure in the conduit Ilia by way of pipe I8 is opposing the pressure'in the conduit 36a.

The piston 52 is provided with a milled slot 54 which engages with a spherical ended lever 55. This lever 55 is mounted and connected toV v a servo valve 56. the servo valve being housed concentrically in the trunnion of the swash plate I2 as shown in Figure 4. The valve is made sensitive to rotational torque by reason of its mounting, the valve is provided at each end with two eep groove ball bearings 51, the outside diameter of which is 5-10 thousandths greater than the diameter of the valve, this assembly being mounted in a parallel bore 58. The valve surface is then clear of the bore surface by a space suii'icient only to accommodate a thin film of oil. The bore.58 is provided with four ports 59 and 60 equally disposed aroundits circumference.` These are adapted to co-operate with diametrically drilled ports in the valve 58. The port apertures in valve 56 are of the same width as the bars 6I separating the ports in the bore 58.

The valve 56 has also a circumferential groove 82 engaging with communicating holes and passages 63 which in turn are connected via conduit 64a to make-up pressure line 64 in which a constant pressure of /120 lbs. is maintained by the pump unit 32.

The lever or arm 55 is constrained by springs 66 and 61 to its centered position. Any effort on the piston 52 due to pressure difference in the cylinders 59 or 53 reacts on one or other of the springs 66 and 61 and by this means the valve 56 is given partial rotation. Movement of the piston 52 moves the part 551 at the spherical end of the pivotal lever or arm 55 (Fig. 1) to rotate said pivotal lever or arm 55 and partially rotate the valve 56. The pivotal level` or arm 55 is provided with two abutments 99, 9i which engage with pivotal levers 92, 93 according to the direction of rotation of said lever or larm 55 and said pivotal levers 92, 93 are Veach provided with a spring 65, 61 anchored to the fixed plate 94. which forms part of the fixed casing of the valve. Adjustable stops 95, 96 are provided on the plate to limit the movements of the levers 92, 93 under the action of their respective springs 66, 61. In the centered position the diametrical ports in the valve 56 are closed by the bars 6I separating the ports 59 and BIJ. It will be seen then, that from this coincidence or centered position any partial rotation of the valve 56 Will cause the diametrical port in said valve, which is in communication with the pressure line 64a, to feed oil into the diametrically opposite ports 59 or 66 according to whichever direction the valve is displaced from its coincidence position.

Leading from the ports 59 and 60 are fluid conduits 68 and 59 which are in communication with each end of a servo cylinder 19.

For the sake of clearness the servo cylinder and servo unit already described are shown as a mirror View that is one part displaced substantially from the other in Fig. 3 of the drawings. A servo piston 1I is housed in the cylinder 10 the piston being connected by means of diametrical drilling 12 to the ball ended lever 13 which is keyed to the swash plate I2. Thus the latter swash plate has the ball ended lever 12 and the aforementioned servo valve 56 diametrically mounted at opposite sides thereof.

Any axial movement of the piston 1I in the cylinder 19 is communicated to the swash plate I2 of the regulator II. The piston 1I is convenriently made hollow to house a pair of centering springs 14 so that when the unit is at rest, i. e. no pressure difference in conduits Illa and Illb, the valve and swash plate I2 are automatically centered.

It will be seen then that any pressure difference in conduits 68 and 69 which is brought about by rotation of the valve 56 will cause the piston-1l to have axial movement in its cylinder 19 and from this, through the medium of lever 13, the swash plate I2 will be moved through an angle which is determined by the angular displacement of the valve 56 by virtue of the fact that the bore 58 is formed in the trunnion of the swash plate I2. Any angular movement of I2 and 58 about the axis of 56 will cause the bars between ports 59 and 66 to close the diametrical port in the valve56 thus arresting the fluid ow ,and restorp1ate l2 at theang1edictatedtbyfthearieularieplacement ,of the .ValveI 5.6: frum'il Centered $3.051-

tion.

Reverse gear is effected by .meanseff. a; ,s.ld.ihs

clutch. 16 keyed -.o.n the output ,'shaftgz Y,and controlled by means ,of :reverse .flever :11.

The clutch .for thefpurposeoftengaging reverse is slid rearwardlmtoiengage thegeargi18- m9unted on a nal drive. shaftilaz-from theJgear-unit In order that:fthe,:torquetmultiplicationof the gear vunit .may 'besmore clearly understood, Eig.-

ure 2 of the drawings is-,aidiagrammaticaview drawn `to Aaccompany Y:the:follow/ting.,explanatory formulae wherein .iA-:power input; t Zzoutput; a, b, cfclV and. e=numbersofiteeth- .icledaetion 'tatie Let R=overallr gearreduction offeomplete .aS- -sembly, and

.pump eepe'eitrper'rev. Mmmm .meterte acitypefrev Then it can .doe fhwnuthatfthe ,pyerailigear reduction when pump and-motorLturn-in fsamedirection, and negative when pi-imp. and motonturn lin.cp posite directions when viewed V.fromV Z. .t Observe also that if -theeXpr-ession in }ccmes..out positive, thenZ and Afturnin-theisame-direction; vif

y negative, Z revolves oppositely to-A.

Whilst theinvention-has beemdescribed-using a differential gear of the-epicyclic-ring.geartypev it will be understood that any suitable differential gear may be employed, providedthree moving elements are present,'the input-shaft, a planet carrier and output shaft.

What I claim is: Y

1. A power transmission,comprising an input shaft, an Output shaft, an epicyclic gear unit having a ring gear, planet pinions and as uringe'ar, said ring gear being operativelyconnectedtQj-the input shaft, means operatively connectingj the planet pinions to the output shaft, a, ho1lovys haft encircling the output shaft andfpperativelvconnected to said sun gear,a; torque unit operatively connected to said hollovvgshaftja hydrauligregulating unit operatively c nnected to sa'dy npu shaft, said torque and regulating units; .be ing communicably connectedby pipelines-that communicate with each other to provide a closed fluid circuit, means for supplying iiuid under pressure to the closed fluid circuit, one of said pipe lines constituting a high pressure main and the other pipe line a low pressure main, a valve unit for controlling communication of the high pressure main with the low pressure main, a control unit communicating with the high pressure main, means operatively connecting the control unit to the regulator unit, and governor means operatively connected to the output shaft and said control unit for operating the latter in accordance with the speed of the output shaft.

t2.. fanowertransmieeien .eeeprieihg en y.tiret eh. tran .output shaft. an. epievelieeeer thitherjlng a ring gear, planetpinionsy and a sun gear, saidrius. seal .beine .Qheretirely eeheeeted .t0 .the input shaft, means operatively connecting the fhlanetnihiene t0 the Outputeheft, e hO'llQW theft encircling the. output vtheft .and .eeeretvelv cen- ;.heetedte Said .Sun geerLe-tereueghit Opere- @lyrconnected tosaid-hollow shaft, a hydraulic .regulating .unit .operatively eehheeted t0 Seid ih- ,put shaft, `said torque and regulating units be- Lllg. C-Qmmuhicably vconnected Vby pipe 4lines 4that communicate with each other to provide aclosed :fluid circuitr neans for supplying fluid under preslrsure',tog-thel closed fluid circuit, one of vsaidupipe linesconstituting a high pressurernain and the other-pipe line a lcvv`- pressure main, `a valve unit yfer ,controlling cemmuheetieh 0f .the high pressureVrnain-withthe lowpressure main, a control .unit communicating with the high .pressure mein. jSeti.d control unit ,includingalow gear control and `a thigh gear control, means `operatively connect- .inggthelowgeer .Control tothe hshpreesuremaih, .meahsoperatively .connecting the 10W gear e011- troltothe regulatorunit for operating lthenlatter -inlOhedirectionLmeans operatively connecting the 'high gear Controlto theregulator unit for operatingythe same in an opposite direction to that of the low'gear control, and governor means operatively connected to the output shaft-and the high gear. control for operatingthe latter in raccordance v,with the speed of v1the output shaft.

lELL-Appeler transmission comprising an input shaft, an output shaft, anepicyclicgearunt hav- ,ingatringgear, planetpiniona and a sun gear,

lsaidring. gearbeingoperatively connected to the inputfshaft .Ineens .operatively connecting the -Dlanet pinionsto theoutput shaft, a hollow shaft ...encircling .-:theoutput shaft and operatively con- .nectedfto .said sungear, a torque unitoperatively connected to saidhollow shaft, ahydraulicregu- .latingunit operatively connectedto said input shaft, said torque and regu1atingunits being .communicably connectedbypipe lines that com- .vmunicate witheachother to provide a closed fluid circuit,x means .for v4supplying, fluid4 under pressure .tothe-.closed fluid. circuit, .oneA of ,said pipe lines constituting ahighA pressure main and ,the vother lpipe line.a'low pressureimainVa valve.u nit for .controlling A.communication pf the high A pressure vmain-.with ithe. 10W, pressure` main, a, control. .unit

communicating with, the. highpressure main, said -Ycontrol unit. including a; low...gearc.ontrol and a .high gear. control, means-.communicatinglthe 10W .gear controlto.thehighpressuremaim a rotary .member operatively ,connected to said regulator unit, meansoperatvely connecting the lowgear vconnecting `the z hig'hagearr control .to the rotary member to operatertheregulator unit'inan op- .positedirection tolthat ofthe low` gear control,

an engine driven pump communicating with said high gear control for supplying fluid pressure thereto, and governor means operatively connected to the output shaft and said high gear control for operating the latter in accordance with the speed of the output shaft.

4. A power transmission comprising an input shaft, an output shaft, an epicyclic gear unit having a ring gear, planet pinions, and a sun gear, said ring gear being operatively connected to the input shaft, means operatively connecting the planet pinions to the output shaft, a hollow shaft encircling the output shaft and operatively con- 1 1 nected to said sun gear, a torque unit operatively connected to said hollow shaft, a hydraulic regulating unit operatively connected to said input shaft, said torque and regulating units being communicably connected by pipe lines that communicate with each other to provide a closed fluid circuit, means for supplying fluid under pressure to the closed fluid circuit, one of said pipe lines constituting a high pressure main and the other pipe line a low pressure main, a valve unit forA controlling communication of the high pressure main with the low pressure main, a control unit communicating with the high pressure main, said control unit including a low gear control and a high gear controlr means communicating the low gear control to the high pressure main, a

rotary member operatively connected to saidregulator unit, means operatively connecting the low gear control to said rotary member for operating the control unit in one direction, means operatively 'connecting the high gear control to the rotary member to operate the regulator unit in an opposite direction to that of the. low gear control, a governor operating means connected to said rotary member for providing a steadying or balancing means for the control unit, and means operatively connected to the output shaft and said high gear control means for operating the latter in accordance with thespeed of the output shaft.

5. A power transmission mechanism according to claim l wherein the valve unit includes a bypass valve operable to cause the fluid pressure to by-pass the regulator unit.

6. A power transmission mechanism according to claim 2 wherein the control unit is inuenced by a couple, one force being applied by fluid pressure in the high pressure main through a connecting pipe to a cylinder and piston connected to the control unit to constitute the low gear n control and the valve unit has a by-pass valve operable to cause the fluid pressure to by-pass the regulator unit.

7. A power transmission mechanism according to claim 2 wherein the control unit is influenced by a couple, one force being applied by uid pressure in the high pressure pipe line through a connecting pipe to a cylinder and piston connected to the control unit to constitute the low gear control, an engine driven pump adapted to supply iiuid at varying pressures to a cylinder having a piston connected to the control unit to constitute the high gear control, and said valve unit having a by-pass valve operable to cause the iiuid pressure to by-pass the regulator unit.

8. A power transmission mechanism according to claim l wherein a two-way relief valve communicates with the valve unit and is adapted to open if the pressure on either side of the fluid circuit reaches a predetermined maximum and thereby by-pass the regulator unit.

9. A power transmission mechanism according to claim 2 wherein the control unit is inuenced by a couple, one force being applied by uid pressure in the high pressure main through a connecting pipe to a cylinder and piston connected to the control unit to constitute the low gear control and a two-way relief valve communicates with the valve unit and is adapted to open if the pressure on either side of the fluid circuit reaches a predetermined maximum and thereby by-pass the regulator unit.

10. A power transmission mechanism according to claim 2 wherein the control unit is influenced by a couple, one force being applied by uid pressure in the high pressure main through a connecting pipe to a cylinder and piston connected to the control unit to constitute the low gear control, an engine driven pump adapted to supply uid at varying pressures to a cylinder having a piston connected to the control unit to constitute the high gear control and a two-way relief valve communicates with the valve unit and is adapted to open if the pressure on either side of the uid circuit reaches a predetermined maximum and thereby by-pass the regulator unit.

1l. A power transmission mechanism according to claim 1 wherein the fluid circulates in a closed circuit in which a predetermined minimum pressure is maintained by means of an engine driven oil pump adapted to deliver oil from a make-up tank into the circuit through non-return valves should the pressure in the circuit fall below the predetermined minimum.

12. A power transmission mechanism according to claim 2 wherein the control unit is influenced by a couple, one force being applied by fluid pressure in the high pressure main through a connecting pipe to a cylinder and piston connected to the control unit to constitute the low gear control, and the fluid circulates in a closed circuit in which a predetermined minimum pressure is maintained by means of an engine driven oil pump adapted to deliver oil from a make-up tank into the circuit through non-return valves should the pressure in the circuit fall below the predetermined minimum.

WILLIAM CULL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,197,789 Bluemel Sept. 12, 1916 1,951,345 Centervall Mar. 20, 1934 1,981,805 Kacer Nov.l 20, 1934 2,139,965 Ljungstrom Dec. 13, 1938 2,153,997 Verderber Apr. l1, 1939 2,173,855 Orshansky Sept. 26, 1939 2,219,052 Orshansky Oct. 22, 1940 2,256,324 Orshansky ISept. 16, 1941 2,285,431 Grossenbacher June 9, 1942 

